Browsing by Subject "oxidation stability"

Microalgae (MA) are a novel feed ingredient for dairy cows. They are an alternative high quality protein source and rich in polyunsaturated fatty acids (PUFA). Supplementation of MA in dairy cow feeds has a potential to increase the amount of beneficial PUFA and bioactive molecules in milk. Four multiparous Finnish Ayrshire cows fed grass silage-based diets were used in a 4 × 4 Latin square with 21-d experimental periods to evaluate the effects of various protein supplements on fatty acid composition, oxidative stability, milk fat globule size and phospholipid content of milk. Dietary treatments consisted of 4 concentrate supplements containing soya (control), or one of three MA supplements: (i) Spirulina platensis, (ii) Chlorella vulgaris or (iii) Chlorella vulgaris + Nannochloropsis gaditana. Inclusion of MA in the diet decreased saturated fatty acid (SFA) content in milk compared to soya and tended to increase monounsaturated fatty acid and PUFA concentrations in milk. MA supplements increased 4:0, 5:0, 6:0, 17:0, 18:1 + trans-15 18:1, and 18:3n-3. Among algae, Chlorella vulgaris lead to highest contents of PUFA and 18:2n-6, Spirulina platensis to highest contents in 14:0, 16:0 and 18:3n-6 and Chlorella vulgaris + Nannochloropsis gaditana to highest contents of 6:0, 20:0 and 20:5n-3 in milk. Oxidation stability and phospholipid content of the milk were not affected by treatment. Diets containing Chlorella vulgaris led to a decrease in the number of milk fat globules, but mean globule diameter (d4,3) and milk fat globule size distribution in terms of volume were unaffected by treatment. Additionally, effects of individual animals on milk fat globule size distribution and phospholipid contents have been shown. In conclusion, MA supplementation moderately increased the content of PUFA at the expense of SFA compared to soya. Enrichment of specific fatty acids depended on the fatty acid composition of the supplement and stronger alterations of milk fatty acid composition will require higher contents of algal fatty acids. Premature spoilage through oxidation was not an issue. Finally, MA fed in the current study could only slightly alter the milk fat globule distribution, but phospholipid contents remained unchanged.